課後習題page101.pp3.7

//************************************************
// triangleArea.java  Author: Jayson 
//***********************************************

import java.util.Scanner;

public class triangleArea 
{
	//--------------------------------------------------
	//  input triangle's three side, and 
	//  output its area with Heron Formula
	//  Heron Formula: area = sqrt(s(s-a)(s-b)(s-c)
	//  s = (a+b+c) / 2
	//--------------------------------------------------
	public static void main(String[] args)
	{
		double a, b, c, s, area;
		Scanner scan = new Scanner(System.in);
		
		System.out.println("Please input three side of a triangle: ");
		a = scan.nextDouble();
		b = scan.nextDouble();
		c = scan.nextDouble();
		scan.close();
		
		s = (a + b + c) /2 ;
		area = Math.sqrt(s * (s-a) * (s-b) * (s-c));
		
		System.out.println("The area of the triangle is: " + area);
	}
}